The present invention relates to a method and apparatus for mapping contoured surfaces. The invention is particularly useful in dental applications, e.g., for preparing artificial dental crowns, and is therefore described below with respect to such an application.
The preparation of an artificial dental crown has historically been a long and expensive process, involving firstly the preparation of a mold, and then the preparation of a crown from the mold. U.S. Pat. No. 4,997,369, in which the inventor of the present application is a joint-inventor, discloses a method and apparatus for producing an artificial dental crown by using a probe which is mounted in the mouth of the patient to receive the crown. The displacements of the probe are measured as the probe is moved along the surfaces of the teeth required to be mapped for preparing the tooth crown. In such a method, however, mounting the movable probe in the mouth of the patient is inconvenient and uncomfortable to the patient. Moreover, mapping teeth surfaces (or other surfaces) by measuring the movements (as distinguished from positions) of the probe produces errors which are cumulative.
An object of the present invention is to provide a method and apparatus for mapping contoured surfaces having advantages in one or both of the above respects and which thereby makes the method and apparatus particularly useful in dental applications.
According to one aspect of the present invention, there is provided a method of mapping a contoured surface, comprising: providing a probe for contacting the contoured surface with at least one light source at a known location with respect to the probe contact surface; providing a light sensor device at a known location with respect to the contoured surface to be mapped; moving the probe over the contoured surface through a plurality of positions with the probe contact surface in contact with the contoured surface at each of the positions; measuring the location in space of each light source at each of the positions; and computing, from the measured location of the light source at each of the positions, the location of the probe contact surface with respect to the known location of the light sensor device.
According to further features in the preferred embodiment described below, the probe is provided with at least three light sources at different known locations with respect to the probe contact surface. Also, the light sensor device includes first, second and third linear arrays of light sensor elements extending along a first axis; and a screen having first, second and third slits. The first and second slits are aligned with the first and second linear arrays of light sensor elements, respectively, but extend along a second axis; and the third slit is aligned with the third linear array of light sensor elements and extends along the first axis. An optical device is provided between the third linear array of light sensor elements and the third slit for diverting the light received from the light sources in the third axis to the first axis.
According to another aspect of the present invention, there is provided apparatus for mapping a contoured surface, comprising: a probe movable to a plurality of positions over and in contact with the contoured surface to be mapped; at least one light source, and preferably three light sources, carried by the probe at different known locations thereof with respect to the contact surface of the probe; a light sensor device mountable at a predetermined location with respect to the contoured surface to be mapped; and a computer controlled by the light sensor device for measuring the locations in space of each of the light sources at each of the plurality of positions, and for computing from the measurements the location of the probe contact surface at each of the positions.
According to further features in the described preferred embodiment, the probe includes a contact detector for detecting the contact of the probe contact surface with the contoured surface to be mapped, and for enabling the computer to measure the locations of the light sources only when the contact detector detects contact of the probe contact surface with the contoured surface.
As will be described more particularly below, although the light sensor device is mounted at a known location with respect to the contoured surface to be mapped, the movable probe is not so mounted, but rather is freely movable over the contoured surface to be mapped. Such an arrangement is particularly useful in dental applications for preparing artificial dental crowns, since an arrangement having an unmounted, freely movable probe is more comfortable to the patient to receive the artificial crown, and is more convenient to the dentist or dental technician for mapping the teeth surfaces to produce the artificial crown. Moreover, such a method and apparatus are inherently capable of higher accuracy since this technique does not produce measurements of the movements of the probe (which measurements would involve cumulative errors), but rather produces direct measurements of the location of the contact surface of the probe at each of the map points, and thereby avoids the cumulation of errors.
Further features and advantages of the invention will be apparent from the description below.